Fig. 8.

The slow afterhyperpolarization (sAHP) duration is increased in aged cholinergic BF neurons. A: superimposed current-clamp records showing an action potential (AP) from a young and an aged cholinergic BF neuron without afterdepolarizations (ADPs: young:gray; aged:black). The spontaneous resting potential is given. B: superimposed current-clamp records as above, except from neurons displaying an ADP. In each case the sAHP of the aged neuron is of longer duration. APs occurred spontaneously without depolarizing current pulses and examples were selected for APs of nearly identical amplitude and duration. Quantitative data are presented in Table 1. C: measurement of the AP amplitude, duration, and threshold is illustrated. Amplitude was measured relative to threshold and duration was measured at threshold. D: an example of the measurement of the sAHP amplitude and duration is shown. Amplitude was measured relative to threshold and duration was measured from the time that the repolarizing phase of the AP crossed the threshold voltage to the time that the potential returned to the pre-AP level. The thick arrow indicates the ADP.